Preparation of ortho-ethyltoluene



Jan 3, 1967 F. J. soDERQUlsT ETAL 3,296,322

PREPARATION OF ORTHO-ETHYLTOLUENE Filed Nov. '7, 1965 Recgc/ea/Canta/9,57l Comp /ex James L, Hm os Rober' H. ,4V/en United StatesPatent O M PREPARATION OF RTHO-ETHYLTOLUENE Frederick J. Soderquist,Essexville, and James L. Amos and Robert H. Allen, Midland, lVlch.,assignors to The Dow Chemical Company, Midland, Mich., a corporation ofDelaware Filed Nov. 7, 1963, Ser. No. 322,089 6 Claims. (Cl. 260-671)This invention concerns an improved method for the preparation ofortho-ethyltoluene from ethylene and toluene starting materials. Morespecifically, the invention concerns a method for the continuouspreparation of mono-ethyltoluene containing a high percentage of theortho isomer.

Polymers prepared from nuclear methylated styrene monomer containing amethyl constituent ortho to the vinyl group display a high resistance toheat distortion. Where vinyltoluene is employed as the monomer, thisproperty increases to a maximum value when pure orthovinyltoluene isemployed. It is therefore advantageous,

in an ethylation of toluene process, to obtain maximum methods for themono-ethylation of toluene generallyV falls within the range of 40-70percent meta, 20-35 percent para and 10-25 percent ortho. Thus, inpreviously known commercial processes, the ortho-ethyltoluene requiredfor the production of ortho-vinyltoluene monomer is a minor constituentof the mono-ethyltoluene product.

It is an object of the present invention to provide an improved methodfor the ethylation of toluene which yields a mono-ethyltoluene productcontaining a high percentage of the ortho isomer. It is another objectof this invention to provide a continuous process for the preparation ofortho-ethyltoluene in commercial quantities. Other objects andadvantages will become apparent after consideration of the followingspecification and claims.

In the general method of the present invention, high yields ofortho-ethyltoluene are obtained ina monoethyltoluene product bycontacting ethylene and toluene in the presence of a suitable catalystunder selected alkylation conditions in a continuous process.

The sole ligure of the accompanying drawing is a schematic diagramrepresenting one embodiment of the present' invention. In this diagramof a continuous process for practice Vof the present invention, toluene,ethylene, and'ethyl chloride are fed at controlled rates into the lowerportion of a reactor equipped with suitable temperature control means. Afresh quantity of a solid Friedel-Crafts catalyst is periodicallyintroduced into the upper portion of thereactor. The solid catalystgranules are retainedon a grid in the reactor until they have reactedwith ethyl chloride to form an activated Friedel-Crafts catalyst whichis a liquid catalyst com- 3,296,322 Patented Jan. 3, 1967 plex. Thisactivated catalyst is continuously withdrawn as it collects at thebottom of the reactor with a portion being optionally recycled into theupper part of the reactor to furnish a part of the catalyst needed forthe alkylation process. Suitable agitation and mixing of the reactorcontents is accomplished by the gas lift effect resulting from theintroduction of ethylene at the bottom of the reactor. Non-condensablegases are withdrawn through an outlet at the top of the reactor. Amixture of reactants and crude alkylate product is removed as an overowthrough an outlet in the upper portion of the reactor. A portion of thisoverflow is preferably recycled to the bottom of the reactor. Thisrecycling permits control of the average residence time of the reactantsin the reactor and facilitates removal of catalyst complex which tendsto settle, in in the recycle leg, in a nondispersed phase that isdelivered to the base of the reactor and withdrawn. The remainder of theoverflow is passed into an aqueous solution which quenches any remainingcatalyst complex present thus preventing further isomerization of thedesired ortho-ethyltoluene product. A fractional distillation process isthen employed to recover the ortho-ethyltoluene fraction.

The ethylation of toluene is effected in the presence of aFriedel-Crafts catalyst, preferably aluminum chloride, which isactivated in known manner with hydrogen chloride or ethyl chloride. Itis an essential feature of the present invention that the liquidcatalyst complex which is thus formed is removed as rapidly as itcollects at the bottom of the reactor since this catalyst complex, whichfacilitates the reaction of ethylene and toluene, also facilitates theisomerization of the ortho-ethyltoluene to the meta and para forms. Therapid removal of the Friedel-Crafts catalyst complex prevents prolongedcontact with the desired isomer product and enables the recovery of highpercentages of ortho-ethyltoluene.

Generally, mild alkylation conditions are employed to minimize the rateof isomerization of the ortho-ethyltoluene initially formed as the majorisomer product. The reactor contents are maintained at a temperature offrom about 25 to 90 C. during the alkylation process with a temperatureof from about to 70 C. preferred. Atmospheric pressure is normally usedalthough higher or lower pressures may be employed.

A quantity of Friedel-Crafts catalyst and recycled catalyst complex inthe range Yof from about 1 to 10 grams per mole of toluene feed isemployed in the method of the present invention with at least a part oithis total consisting of fresh catalyst which is periodically added tothe reactor during the continuous alkylationprocess together withhydrogen chloride or ethyl chloride to yield the activated catalyst.

A quantity of from about 1.5 to 6 moles of toluene per mole of ethyleneis employed. Although a higher ratio of toluene may be employed, thereis no advantage in doing so.

The average residence time of the reactants in the reactor may rangefrom about ten minutes to ten hours although a time of from about two tosix hours is preferred.

The various conditions discussed above are inter-related and optimumvalues of one condition depend on those valuesl adopted for others.Thus, when larger amounts of catalyst are employed, lower temperaturesand residence times may be suitable. Conversely, as the temperature isincreased, less catalyst and/ or a shorter residence time is necessaryt-o achieve the desired results.

The following examples describe completely representative specicembodiments of the present invention. These examples, however, are notto be interpreted as limiting the invention other than as dened in theclaims.

EXAMPLE 1 A quantity of 276 grams of toluene per hour was metered intothe bottom portion of a reactor at a constant rate by means of apositive displacement pump. A quantity of 15.5 grams per hour ofcylinder ethylene was lsimultaneously fed at a controlled rate via amanometer, through a wet test meter, through a dryer and nall-y to aninjection port at the extreme bottom of the reactor. Aluminum chlorideand ethyl chloride were fed into the reactor at rates equal to 5.0 and2.5 grams/hour, respectively. The reactor was equipped with heating andcooling means land contained a grid about four inches above the reactorbottom to support the lperiodically added aluminum chloride crystalsuntil they had reacted with the ethyl chloride to form liquid catalystcomplex. The complex so formed was removed from the bottom of thereactor as rapidly as it accumulated.

During the course of this continuous reaction the temperature wasmaintained at 60 C. Non-condensible gases were withdrawn through areflux condenser, conducted to an HC1 scrubber and then to a wet testmeter before being vented to the atmosphere. Crude alkylated product wascontinuously withdrawn from the reactor by a simple overflow outlet nearthe t-op of the reactor and conducted through a trap leg to a coolingcondenser and into a wash and decanting vessel. In this Vessel the crudealkylate was contacted with wash Water to remove the last traces ofcatalyst. The crude product was then separated into its variouscomponents by fractional distillation.

Approximately 19 Weight percent of the crude allkylate wasmono-ethyltoluene with an isomer distribution of 38.5 percent ortho,33.7 percent meta and 27.8 percent para.

EXAMPLE 2 In Table I, below, the conditions employed in a series ofexperiments, utilizing the method of the present invention, aretabulated. The rate of feed of ethylene and catalyst, the temperaturemaintained during the alkylation and the amount of catalyst complexrecycled were varied. In -a number of runs a quantity ofpolyethyltoluene byproduct was recycled and introduced with the reactantfeed -to determine whether the production of ortho-ethyltoluene would beeffected. Table Il, below, shows the crude alkylate composition and theisomer distribution of the mono-ethyltoluene product fraction in each ofthe experimental runs listed in Table I.

Table I [Feed rates-grams per hour l] Run Catalyst Mol ratio, No. Temp.02H4 AlCl; Complex Polyethyltoluenes 01H4:

Toluene 1 The feed rate of toluene in each run was 276 grams per hour.The

feed rate of ethyl chloride in each run was 2.5 grams per hour.

Table III Complexed Hydrocarbon Analysis, Weight Percent ComplexedCatalyst Run N o. Removal Ethyltoluene Rate, g./hr. Toluene Ortho Metaand Poly Para 1 l0 21. 1 2. 7 -8. 3 47. 6 2- 15.9 50. 4 3. 1 26. 0 20. 54() 3- 32 38. 9 1. 7 4. 8 54. 3 4---- 75 31. 4 3.0 25. 4 40.2 5-..- 9462.1 5.1 24.8 8.0 6 9 37. 8 2. 0 17. 0 43. 2 7. 23. 7 40. 1 2. 0 17. 540.4 8. l5 32. 7 2. 7 24. 0 40. 6 9 45 51. 3 2. 1 18. 7 27. 9 10- 15 57.4 `2. 0 17. 8 22. 7 11 3o s. 9 4. e 41. 7 44. s 12 30 32. 2 3. 5 31. 532. 8

We clama: 1. A continuous process for preparing ortho-ethyl t Table IICrude Product Analysis- Isomer Wt. Percent Distribution-Mono-Ethyltoluene Run No. Fraction Ethyltoluene Toluene Ortho Meta ParaPoly Ortho Meta Para 78.6 7. 2 6. 3 5. 2 2. 7 3S. 5 33. 7 27.8 81. 0 6.7 5. 1 4. 5 2. 7 41.1 3l. 3 27.6 79. 5 7. 0 4. 3 4. 9 4.3 43. 2 26. 530. 3 69.0 8. 7 8. 9 7. 8 5. 6 34. 2 35. 0 30.8 71. 5 9. 2 4. 6 5. 9 8.8 46. 7 23. 3 30. 0 79. 1 5. 5 8. 2 5. 3 l. 9 28. 9 43. l 28. 0 78. 2 6.2 4. 6 4. 8 6. 2 39.8 29. 5 30. 7 70. 4 7. 8 8.6 8.4 4. 8 31. 5 34. 733. 8 78. 6 6. S 4. l 4. 9 5. 6 43. 0 25. 9 3l. l 74. 7 7. 3 8. 0 6. 73.3 33. 2 36. 4 30. 4 81.6 6. 7 4. 0 4. 2 3. 5 45.0 26. 9 28. l 75. 3 8.2 5.8 6. 3 4. 4 40. 4 28. 6 31.0

EXAMPLE 3 In each of the experiments of Example 2, Le., Run Nos. l-12,the catalyst complex n-ot recycled was accumulated and analyzed. Theseresults indicate the trend towards isomerization of the ortho isomerwhen allowed to remain in prolonged contact with the catalyst complex.

grams of an activated Friedel-Crafts catalyst per,4

mole of toluene fed to said reaction zone,

(C) removing all of said activated catalyst settling out of saidreaction zone in a non-dispersed phase immediately upon formationthereof,

(D) withdrawing a mixture of unreacted toluene, mono-ethyltoluene andpolyethyltoluenes from said reaction zone at a rate which provides foran average residence time of said reactants of from about 10 minutes to10 hours,

(E) neutralizing any of said catalyst present in said mixtureimmediately upon withdrawal thereof, and

(F) separating said mixture by fractional distillation whereby animproved yield ofortho-ethyltoluene product is obtained.

2. The method of claim 1 wherein said activated Friedel-Crafts catalystis activated aluminum chloride.

3. The method of claim 2 wherein said temperature is from abeut 50 te79' C.

4. The method of claim 3 wherein said average residence time is fromabout six to eight hours.

5. The method of claim 1 wherein a portion of said activated catalystremoved is recycled through said reaction zone.

6. The method of claim 1 wherein a portion of said mixture of toluene,mono-ethyltoluene and poly-ethyltoluenes withdrawn from said reactionzone is recycled into said reaction zone.

References Cited by the Examiner UNITED STATES PATENTS 4/ 1940 Amos etal 260-671 9/ 1956 Amos et al. 260-671

1. A CONTINUOUS PROCESS FOR PREPARING ORTHO-ETHYLTOLUENE, WHICH PROCESSCOMPRISES: (A) FEEDING ETHYLENE AND TOLUENE REACTANTS IN A RATIO OFABOUT 1.5 TO 6.0 MOLES OF TOLUENE PER MOLE OF ETHYLENE, INTO A REACTIONZONE MAINTAINED AT A TEMPERATURE OF FROM ABOUT 20* TO 90*C., (B)PROVIDING A DISPERSION OF FROM ABOUT 1 TO 10 GRAMS OF AN ACTIVATEDFRIEDEL-CRAFTS CATALYST PER MOLE OF TOLUENE FED TO SAID REACTION ZONE,(C) REMOVING ALL OF SAID ACTIVATED CATALYST SETTLING OUT OF SAIDREACTION ZONE IN A NON-DISPERSED PHASE IMMEDIATELY UPON FORMATIONTHEREOF,